Process for refining mineral oils



Dec. 1, 1936. T EZ N K. 2,062,733.

PROCESS FOR REFINING MINERAL OILS Filed D90. 23, 1933 0/1. Ac/D a 6 ACID TREATING d TANK 1 STRONG ALKA L/ /f e K A REACI'ION II L CHAMBER I KEHNEO OIL V V 3 SOAP SOAPXAL/(AL/ 2+ ALAAH nwcwrafi W/T/VESSJ. 0 f 60f 6c/13 f6 72 6 fi 5y -.r/

aw. Afro/M's v Patented Dec. 1, 1936 UNITED STATES PROCESS FOR REFINING MINERAL OILS George J. Strezynski, Poughkeepsie, N. Y., as-

signor to The De Laval Separator Company, New York, N. Y., a corporation of New, Jersey Application December 23, 1933, Serial No. 703,768

Claims.

My invention relates to those processes for refining mineral oils which involve treatment with a mineral acid, usually sulfuric acid, followed by treatment with alkali, usually caustic soda, to

5 neutralize free acid.

The object of the invention is to substantially reduce the time of treatment and to save reagents, thereby reducing the cost of refining oils 7 particularly in the steps including treatment with 'acid, washing and neutralizing.

A typical process that has been long in use includes addition of acid to oil in large tanks and agitation by blowing with air for from a few minutes to an hour or more, followed by gravity settling, which may require from two to sometimes as much as forty-eight hours. This is followed by Washing with water sprayed on the top of the tank and allowed to settle through the oil, sometimes repeated as much as three times. The oil is then treated with alkali to neutralize remaining traces of acid, followed by more washing to remove the excess alkali.

Because of imperfect mixing it is necessary to use excessive quantities of both acid and alkali and to leave each reagent in contact with the oil for a long time. These operations result in waste of both reagents and, by the time that all of the oil has been reacted on sufiiciently, some of the oil has had extreme treatment and is considered by refiners to be off color. There is also a tendency for some of the oil to become emulsified with the water and lost.

To reduce over-treatment and discoloration by the long contact of alkali with oil, the usual practice is to use very dilute alkali (e. g., 3 B.). This must necessarily be used in large excess (sometimes as much as ten times the quantity required for neutralization of acid bodies in the oil), and because it forms a permanent emulsion with the soaps formed, none of the excess alkali can be reclaimed. This soap-alkali emulsion also has a strong tendency to emulsify with the oil, causing a serious oil loss in addition to the waste of alkali.

My invention comprises a process whereby the neutralization may be economically effected and the separation of the purified oil greatly expedited by treating the oil with a reagent comprising strong caustic soda (20-50 B.) and a small percentage of triethanolamine. The most successful execution of the process requires a preliminary treatment with a mineral acid, a twostage separation of acid sludge from the oil and a short time contact between the oil and caustic. soda so as to avoid injury to the oil. The caustic soda in excess of the amount actually needed for neutralization may be separated from the treated oil and the soaps formed and can be used for treating other quantities of oil.

The preferred manner of carrying out my improved process is as follows. After acid treating in any of the well known ways and separation of most of the sludge from the oil, the oil is centrifuged to remove, as far as possible, the remaining pepper sludge. Proportional streams of oil and the above specified reagent are then fed into a device (which may be a centrifugal pump), where they will be intimately mixed. Thence the mixture is fed, either directly, or (if necessary to give more timefor the reaction) through a small reaction chamber, into a centrifugal separator, where the oil is separated from the soaps formed and any residual alkali. The soap and alkali may flow into a tank, where the soap will collect on top, while the alkali may be drawn from the bottom and returnedto the mixer for use with more acid-treated oil.

I have found that oil so treated is equal to or better than that produced by the old space-occupying and time-consuming batch process and that very little, if any, oil is lost in emulsions. In addition, the soaps formed float on, and may be skimmed oil. from, the top of any unused alkali, which, as above stated, may then be used for the treatment of another quantity of acid-treated oil.

When extremely high quality oil is desired, it may be given one water wash in the present manner.

The drawing is a diagram of an apparatus in which my improved process is adapted to be practiced.

The oil is fed from a source a and the acid from a source 1), into a tank 0, wherein the mixture is agitated and washed as above described. This treatment may be a batch treatment or a continuous treatment. The acid sludge may be withdrawn through pipe 11 and the oil run through a centrifugal separator e to remove, as far as possible, the pepper sludge. The oil, together with a proportionate stream of the reagent comprising soda and a small amount of triethanolamine from a supply tank 1 is run through any mixing apparatus (which may be a centrifugal pump 9 and beyond that a reaction chamber h). The mixture of oil and reagent then flows into a centrifugal separator k, where the oil and alkali sludge are separated, the refined oil being discharged through pipe m and the alkali sludge into a tank n, whereinthe soap will collect on top, while the alkali may be drawn from the bottom and returned through pipe 0 to the mixer or alkali supply. Instead of separating the soap and alkali by gravity, they may be centrifugally separated.

If, as above described, a small proportion (1-5%) of triethanolamine be added to the al kali (caustic soda), the resultants from the reaction between them (which takes place immediately) will so act on the oil that the mixture may be fed tothe centrifugal separator at a greatly increased rate and still effect practically complete separation of the soap and alkali from the oil.

I have also found that the addition of sodium metasilicate to strong caustic soda will, without reducing the specific gravity needed for complete separation, make it easier and safer to handle and also produces a sludge that is plastic instead of a granulated dispersed carbon.

The term strong, as herein applied to alkali or alkaline solutions or reagents, is intended to include all solutions having a density of 20 B. or greater.

What I claim and desire to protect by Letters Patent is:

1. The process of refining oils which includes treating the oil with a mineral acid, adapted to form a separable sludge, treating the acidtreated oil with a reagent comprising caustic soda having a density not less than 20 B. sodium metasilicate and a relatively small percentage of triethanolamine, and separating the thus treated oil from the reagent and reaction prodnets.

2. The process of refining oils which includes treating the oil with a mineral acid adapted to form a separable sludge, separating a portion of the sludge from the oil, centrifugally separating from the partlydesludged oil so much of the remaining pepper sludge as may be so removed,

mechanically mixing a stream of the oil continuously flowing from the centrifuge with a continuously flowing stream of a reagent comprising a caustic soda solution having a density not less than 20 B. and containing a small percentage of triethanolamine and continuously cer itrifug ally separating the alkali sludge from the soda-treated oil.

3. The process of refining oils which includes treating the oil with a mineral acid adapted to form a separable sludge, treating the acid-treated oil with a reagent comprising caustic soda having a density not less than 20 B. and a minor proportion of triethanolamine and separating the thus treated oil from the reagent and reaction products.

4. The process of refining oils which includes treating the oil with a mineral acid adapted to form a separable sludge, separating a portion of the sludge from the oil, centrifugally separating from the partly desludged oil as much of the remaining pepper sludge as may be so removed, mechanically mixing a stream of the oil continuously flowing from the centrifuge with a continuously flowing stream of a solution having a density of 20 to B. in which the chemicals comprise caustic soda, metasilicate of soda and triethanolamine, continuously separating the solution and reaction products from the oil, separating the reaction products and the solution and flowing the stream of solution to said locus of mechanical mixing.

5. The process of refining oils which includes treating the oil with a mineral acid adapted to form a separable sludge, separating most of the sludge from the oil, mixing the partly desludged oil with a reagent comprising a caustic soda solution having a density of not less than 20 B. and a minor proportion of triethanolamine and separating the thus treated oil from the reagent and reaction products.

GEORGE J. STREZYNSKI. 

